The Reagan administration has begun trying to scrap machinery set up in recent years to remove water projects from pork-barrel politics.

The effort, if successful, would gut some of the most significant water policy changes made under the Carter administration, and give Interior Secretary James G. Watt additional power to decide what projects should be built.

The administration has indicated it intends to repeal an intricate set of "principles and standards" that the Corps of Engineers and other agencies had to meet to justify dams, reservoirs and port and river dredging projects. It has also dropped environmental quality as a major water policy objective and abandoned machinery that was set up--though never funded--for the independent review of water projects.

It is replacing regulations, set out in the principles and standards, with "flexible guidelines," according to officials. The nonbinding guidelines can be waived completely for agencies with approval of the Cabinet Council on Natural Resources, now headed by Watt.

The purpose is "to reduce the burden on agencies in complying with detailed and lengthy binding technical rules," according to a notice of the change in the Federal Register. The rules, it added, "are too complicated, too rigid, and too cumbersome."

Environmental groups, which helped write the rules, see the change as a major retreat. They fear the shift will greatly enhance Watt's role in national water policy, and enable him to push through a series of water projects in the West, which can't be justified economically under current rules.

"All the effort to remove water resources from pork barrel is being lost," says Brent Blackwelder of the Environmental Policy Center. "Jim Watt will be in a position where he can use pork barrel whenever it becomes politically expedient."

Edward Dickey, a government economist working on the changes, argues these fears are groundless. He says the Cabinet council, made up of four Cabinet members, will be extremely tough on waiving guidelines. Proponents of development, he adds, find this provision "shockingly restrictive."

The changes, Dickey says, represent a "basic philosophical difference in how you want government to work." By his account, the Carter administration favored a "set of very rigid technical steps, and an independent review" to weed out bad projects before they were sent to Congress. President Reagan, on the other hand, wants to get rid of unnecessary red tape and studies "so we can focus on the problem at hand--how to get the best water projects possible."

Some of President Carter's earliest, and most bitter battles with Congress were over water projects he wanted to scrap. In an attempt to remove them from politics, he proposed setting up an independent review system in the Water Resources Council. Congress, however, refused to fund the independent review, although the council did serve as the coordinator for the agencies' projects.

Reagan signed an executive order last month eliminating the independent review function. Simultaneously, Watt signed a memo repealing the principles and standards along with two detailed manuals setting out procedures for evaluating the cost and benefits of water projects.

Meanwhile, environmental groups have launched a counteroffensive, attempting to organize opposition to the changes. They argue there is no evidence the current rules, which are designed to save the government money, have delayed projects, and the changes are being made simply for the convenience of government agencies.

As they have in the past, environmental groups are directing their attacks at Watt. In one call-to-arms letter, Edward Osann, coordinator of the Coalition for Water Projects, which includes 24 groups, says: "Let's send James Watt the message. Sound water projects: Yes! Pork barrel projects: No!"

In another letter, Osann notes Reagan himself will eventually have to sign off on the changes. "This issue will provide an important test of how closely the president is willing to associate himself with the compulsive developmental policies of Secretary Watt," he adds.